Heat pump air conditioner

ABSTRACT

A heat pump air conditioner includes an intake side heat exchanger including heat transfer pipes passing a refrigerant and being arranged in a direction along an air inlet face, intake heat exchanger configured to cool or warm air and supply the air to a space. A plurality of heat pumps include a plurality of compressors and configured to compress the refrigerant and supply the compressed refrigerant to the heat transfer pipes and a plurality of heat side exchangers and connected to the respective compressors, the heat pumps sharing the air intake side heat exchanger, and a controller configured to switch a state of the compressors and between an operating state and an operation stopped state. The controller controls the compressors and to switch an operation of each of the compressors and between starting and stopping in accordance with a magnitude of an air-conditioning load.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat pump air conditioners.

2. Description of the Related Art

As described in Japanese Laid-Open Patent Application Publication No. H09-264614, a conventional heat pump air conditioner includes a compressor, an air-intake-side heat exchanger, and a heat-source-side heat exchanger. The compressor and heat exchangers form a heat pump, and are connected to each other by piping, such that a refrigerant circulates through these devices.

Such a heat pump air conditioner is used throughout the year. In the description below, within one year, a period other than a high-temperature summer period and a low-temperature winter period is referred to as an intermediate period.

In a conventional heat pump air conditioner, the higher the necessary cooling/heating capacity of the heat pump air conditioner, the higher the minimum critical power of the compressor. Therefore, the cooling/heating capacity may be too high in such a period as the intermediate period in which a load applied to the air conditioner is small. As a result, in such a period as the intermediate period, a cooling/heating operation is stopped. In this case, however, cooling/heating effects cannot be exerted. Thus, cooling and heating may become excessively strong or insufficient. This causes an increase in wasteful energy consumption of the compressor. Consequently, the comfortableness and energy efficiency of the cooling and heating are degraded.

An object of the present invention is to provide a heat pump air conditioner capable of improving the comfortableness and energy efficiency.

SUMMARY OF THE INVENTION

In order to solve the above-described problems, a heat pump air conditioner according to a first aspect of the present invention includes: an air-intake-side heat exchanger including a plurality of heat transfer pipes through which a refrigerant passes, the heat transfer pipes being arranged in a direction along an air inlet face of the air-intake-side heat exchanger, the air-intake-side heat exchanger being configured to convert intake air into cool air or warm air and supply the cool air or warm air to a space to be air conditioned; a plurality of first and second heat pumps including, at least, a plurality of compressors configured to compress the refrigerant and supply the compressed refrigerant to the heat transfer pipes and a plurality of heat-source-side heat exchangers connected to the respective compressors, the first and second heat pumps sharing the air-intake-side heat exchanger; and a controller configured to switch a state of the compressors between an operating state and an operation stopped state. The controller controls the compressors to switch an operation of each of the compressors between starting and stopping in accordance with a magnitude of an air-conditioning load.

According to the first aspect of the present invention, the plurality of heat pumps share the load for realizing a necessary cooling/heating capacity of the heat pump air conditioner. Therefore, in a case, for example, where the air-conditioning load is small, only one of the compressors is caused to operate, and thereby cooling/heating can be performed by only one of the heat pumps. This makes it possible to reduce wasteful energy consumption of the compressors in a case where the air-conditioning load is small, thereby improving the comfortableness and energy efficiency of the cooling/heating.

According to a second aspect of the present invention, among the plurality of heat transfer pipes, a plurality of heat transfer pipes connected to the first heat pump serve as first heat transfer pipes, and a plurality of heat transfer pipes connected to the second heat pump serve as second heat transfer pipes. The plurality of first heat transfer pipes and the plurality of second heat transfer pipes are arranged such that, in the one direction, one first heat transfer pipe and one second heat transfer pipe are arranged alternately, or two first heat transfer pipes and two second heat transfer pipes are arranged alternately.

Assume a case where the first heat transfer pipes or the second heat transfer pipes are unevenly distributed and concentrated in one area along the air inlet face. In this case, when cooling/heating is performed by only one of the heat pumps, the cooling/heating is performed in an uneven manner utilizing only one part of the air-intake-side heat exchanger. In this case, air passing through the air-intake-side heat exchanger is partly cooled down or heated up, and thereby unevenness occurs in the heating or cooling of the air. In this respect, the air passing through the air-intake-side heat exchanger can be evenly heated up or cooled down by arranging the first heat transfer pipes and the second heat transfer pipes such that, in one direction, one first heat transfer pipe and one second heat transfer pipe are arranged alternately, or two first heat transfer pipes and two second heat transfer pipes are arranged alternately.

According to a third aspect of the present invention, the controller causes at least a pair of the compressors to operate alternately. In this manner, a situation can be prevented where only one of the heat pumps is operated excessively. This makes it possible to extend the life of the heat pump air conditioner and reduce the life cycle cost of the heat pump air conditioner.

Since the pair of the compressors can be caused to operate alternately by merely switching operation patterns by the controller in accordance with software, the alternate operation can be readily realized. Therefore, installation of additional devices such as a timer is unnecessary, which realizes cost reduction.

According to a fourth aspect of the present invention, before causing the pair of the compressors to operate alternately, the controller totals either a previous operating time of each of the compressors or the number of previously performed operations of each of the compressors, and the controller preferentially causes one of the compressors with a less previous operating time or a less number of previously performed operations to operate. In this manner, a situation can be prevented where one of the compressors is heavily operated disproportionately, and thereby the operating time or the number of performed operations can be made uniform among all of the compressors. This makes it possible to extend the life of the heat pump air conditioner and reduce the life cycle cost of the heat pump air conditioner.

According to a fifth aspect of the present invention, the controller switches a state of the pair of the compressors between an operating state and an operation stopped state not in a defrosting operation period during a heating operation, but in a period other than the defrosting operation period. Accordingly, in the defrosting operation period during the heating operation, the pair of the compressors does not stop at one time, but the compressors are defrosted alternately. Therefore, the heating operation is not interrupted. Also, it is not necessary to separately install a heater or the like for use in the defrosting operation.

According to a sixth aspect of the present invention, after causing the second heat pump to start operating, when causing the first heat pump to start operating, the controller controls the operation of the second heat pump to reduce an output of the second heat pump, such that an output of the first heat pump when the first heat pump starts operating is subtracted from the output of the second heat pump, which has already started operating. In this manner, increase/decrease in the outputs of the plurality of heat pumps can be offset, and thereby overshoot can be eliminated. This makes it possible to reduce unevenness in cooling/heating, thereby realizing stable air conditioning.

According to a seventh aspect of the present invention, in a stop operation of causing an output of the first heat pump to decrease in accordance with elapse of time and then causing an output of the second heat pump to decrease in accordance with elapse of time, the controller controls the operation of the second heat pump such that, when the first heat pump stops operating, the output of the second heat pump increases by an amount corresponding to a decrease in the output of the first heat pump, the decrease occurring immediately before the first heat pump stops operating. In this manner, increase/decrease in the outputs of the plurality of heat pumps can be offset, and thereby undershoot can be eliminated. This makes it possible to reduce unevenness in cooling/heating, thereby realizing stable air conditioning.

According to an eighth aspect of the present invention, the plurality of first and second heat pumps have different minimum critical powers from each other. For example, assume a case where the ratio of the minimum critical power of the first heat pump to the minimum critical power of the second heat pump is 6:4. In this case, if the air-conditioning load is small, then only the heat pump with a lower minimum critical power, i.e., the second heat pump, may be operated. On the other hand, assume a case where all the heat pumps have the same minimum critical power, for example, the ratio of the minimum critical power of the first heat pump to the minimum critical power of the second heat pump is 5:5. In this case, unlike the case where each heat pump has a different minimum critical power, a suitable operation for a small air-conditioning load cannot be performed. Thus, according to the eight aspect of the present invention, since each heat pump has a different minimum critical power, a suitable operation can be performed even if the air-conditioning load varies widely. This consequently makes it possible to improve the comfortableness and energy efficiency of cooling/heating.

According to a ninth aspect of the present invention, the heat pump air conditioner further includes a vaporizing humidifier and a steam humidifier. In the heat pump air conditioner, along an air passage, the vaporizing humidifier is disposed downstream of the air-intake-side heat exchanger, and the steam humidifier is disposed downstream of the vaporizing humidifier. The vaporizing humidifier and the steam humidifier are connected to the controller. The controller causes the vaporizing humidifier to humidify intake air, and then if the humidifying of the intake air by the vaporizing humidifier is insufficient, causes the steam humidifier to operate to further humidify the intake air. Accordingly, at the time of humidifying the air, the air conditioner mainly uses the vaporizing humidifier whose running cost is less than that of the steam humidifier. Therefore, by humidifying the air by the vaporizing humidifier first and then compensating for the shortfall of the humidity by the steam humidifier, the cost of humidifying the air can be reduced.

According to a tenth aspect of the present invention, a cross section of each heat transfer pipe has an ellipsoidal shape. Accordingly, the air flow resistance of the heat transfer pipes is small. Therefore, pressure loss in the air passing by the heat transfer pipes is small. Since the area of contact between the heat transfer pipes and the air passing by the heat transfer pipes can be set to be large, the efficiency of heat exchange between the heat transfer pipes and the air passing by the heat transfer pipes can be improved, which makes it possible to improve the comfortableness and energy efficiency of the cooling/heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing an overall configuration of a heat pump air conditioner according to the present invention.

FIG. 2 is a perspective view showing an internal structure of an air-intake-side heat exchanger.

FIG. 3 is a plan view of the air-intake-side heat exchanger of FIG. 2.

FIGS. 4A and 4B show examples of arrangement of first and second heat transfer pipes of the air-intake-side heat exchanger, and show views obtained when FIG. 2 is seen from the front.

FIG. 5A shows control steps from when heat pumps are in an operation stopped state to when the outputs of the heat pumps reach their upper limits, and FIG. 5B shows control steps from when the heat pumps are in an operating state to when the heat pumps become an operation stopped state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a heat pump air conditioner according to one embodiment of the present invention is described with reference to the drawings. In the drawings, the same or corresponding elements are denoted by the same reference signs, and repeating the same descriptions is avoided below.

FIG. 1 is a front view showing a schematic configuration of a heat pump air conditioner 200 according to the present embodiment. The heat pump air conditioner 200 includes: a casing 1 in which an air inlet 18 and an air outlet 19 are formed; an air blower 14 for supplying air; an air-intake-side heat exchanger 3 provided with an air inlet face 13; first and second compressors 2 a and 2 b for compressing and conveying a refrigerant; and heat-source-side heat exchangers 4 a and 4 b. The heat pump air conditioner 200 further includes: first and second heat pumps 5 a and 5 b, which share the air-intake-side heat exchanger 3 and have a cooling function and a heating function; a vaporizing humidifier 6 disposed downstream of the air-intake-side heat exchanger 3; a steam humidifier 7 disposed downstream of the vaporizing humidifier 6; and a controller 8 configured to control operations of these devices. The minimum output necessary for the first heat pump 5 a to start operating is different from the minimum output necessary for the second heat pump 5 b to start operating. That is, the first and second heat pumps 5 a and 5 b have different minimum critical powers from each other. Specifically, the ratio of the minimum critical power of the first heat pump 5 a to the minimum critical power of the second heat pump 5 b is 6:4. The ratio is of course not limited to 6:4.

The inlet 18 of the casing 1 is formed such that the opening of the inlet 18 faces the air inlet face 13. Air that has entered the casing 1 through the inlet 18 enters the air-intake-side heat exchanger 3 through the air inlet face 13, and exchanges heat with a refrigerant in the air-intake-side heat exchanger 3 to become cool air or warm air. Thereafter, the cool air or warm air is supplied to a space to be air conditioned (e.g., a room) through the outlet 19 of the casing 1. The air for use in air conditioning (hereinafter, “air-conditioning air”) flows in a flow direction F.

The first heat pump 5 a repeats a compression process, a condensation process, an expansion process, and an evaporation process of a refrigerant in this order, the refrigerant circulating inside the first heat pump 5. In the evaporation process, the first heat pump 5 a absorbs heat from air that exchanges heat with the refrigerant. In the condensation process, the first heat pump 5 a releases heat to air that exchanges heat with the refrigerant.

The first heat pump 5 a includes: the heat-source-side heat exchanger 4 a configured to perform either one of the evaporation process or the condensation process, which is different from a process performed by the air-intake-side heat exchanger 3; the first compressor 2 a configured to perform the compression process; a decompression mechanism 9 a, such as an expansion valve, configured to perform the expansion process; and a switching mechanism 10 a, such as a valve, configured to switch a process to perform between the evaporation process and the condensation process. The first compressor 2 a, the switching mechanism 10 a, the heat-source-side heat exchanger 4 a, and the decompression mechanism 9 a are connected via piping, and the refrigerant circulates through the inside of these.

The second heat pump 5 b also repeats the four processes of compression, condensation, expansion, and evaporation of a refrigerant in this order, the refrigerant circulating inside the second heat pump 5 b.

The second heat pump 5 b includes: the heat-source-side heat exchanger 4 b configured to perform either one of the evaporation process or the condensation process, which is different from a process performed by the air-intake-side heat exchanger 3; the second compressor 2 b configured to perform the compression process; a decompression mechanism 9 b, such as an expansion valve, configured to perform the expansion process; and a switching mechanism 10 b, such as a valve, configured to switch a process to perform between the evaporation process and the condensation process. The second compressor 2 b, the switching mechanism 10 b, the heat-source-side heat exchanger 4 b, and the decompression mechanism 9 b are connected via piping, and the refrigerant circulates through the inside of these.

FIG. 2 is a perspective view showing an internal structure of the air-intake-side heat exchanger 3. FIG. 3 is a plan view of the air-intake-side heat exchanger 3 of FIG. 2. The air-intake-side heat exchanger 3 includes: a large number of heat exchanger plates 11, which are arranged in the front-back direction and provided with gaps in between in a manner to allow air from the flow direction F to pass through; and a large number of first and second heat transfer pipes 12 a and 12 b, through which the refrigerant flows and which are arranged vertically in parallel to each other and fitted to the heat exchanger plates 11. The first heat transfer pipes 12 a are connected to the first heat pump 5 a, and the second heat transfer pipes 12 b are connected to the second heat pump 5 b.

As shown in FIG. 3, each of the heat transfer pipes 12 a and 12 b is formed by lining up pipe elements 100 in the transverse direction, the pipe elements 100 being bent so as to be in contact with the heat exchanger plates 11. Each pipe element 100 includes: a first portion 110 extending from a refrigerant inlet/outlet side toward the back perpendicularly to the flow direction F of the air-conditioning air; a second portion 120 extending short in parallel to the flow direction F from the back end of the first portion 110; and a third portion 130 extending in parallel to the first portion 110 from the end of the second portion 120 toward the refrigerant inlet/outlet side. That is, the first and second heat transfer pipes 12 a and 12 b are long in a direction perpendicular to the flow direction F of the air-conditioning air, i.e., the first and second heat transfer pipes 12 a and 12 b are of a counter-flow type.

When the refrigerant flows through the first and second heat transfer pipes 12 a and 12 b, the refrigerant and the air flowing through the gaps between the heat exchanger plates 11 exchange heat with each other via the first and second heat transfer pipes 12 a and 12 b and the heat exchanger plates 11. As previously described, the first and second heat transfer pipes 12 a and 12 b are of a counter-flow type. However, as an alternative, the first and second heat transfer pipes 12 a and 12 b may be of a cross-flow type. The cross section of each of the first and second heat transfer pipes 12 a and 12 b has an ellipsoidal shape (see FIGS. 4A and 4B) such that the air flow resistance of the heat transfer pipes 12 a and 12 b is reduced, and such that the area of contact between the heat transfer pipes 12 a and 12 b and the air passing by the heat transfer pipes 12 a and 12 b is set to be large. However, as an alternative, the cross section of each of the first and second heat transfer pipes 12 a and 12 b may have a round shape.

Similar to the air-intake-side heat exchanger 3, the heat-source-side heat exchangers 4 a and 4 b are formed by fitting a large number of heat transfer pipes to a large number of heat exchanger plates, which are provided with gaps in between in a manner to allow air to pass through. The heat-source-side heat exchangers 4 a and 4 b include air blowers 15 a and 15 b for ventilation.

FIGS. 4A and 4B show examples of arrangement of the first and second heat transfer pipes 12 a and 12 b of the air-intake-side heat exchanger 3. FIGS. 4A and 4B show views obtained when FIG. 2 is seen in a direction G, i.e., seen from the front. In FIGS. 4A and 4B, white outlined heat transfer pipes are the first heat transfer pipes 12 a, and blackened heat transfer pipes are the second heat transfer pipes 12 b. As indicated by dotted lines in FIGS. 4A and 4B, each of the heat transfer pipes 12 a and 12 b has a shape that is continuously bent upward and downward in an alternate manner in the flow direction F of the air-conditioning air. Specifically, the third portions 130 are positioned higher than the first portions 110. By forming each of the heat transfer pipes 12 a and 12 b to have a shape that is continuously bent upward and downward in an alternate manner, the length of each of the heat transfer pipes that come into contact with the air-conditioning air is increased.

In FIG. 4A, the first heat transfer pipes 12 a and the second heat transfer pipes 12 b are arranged such that, in the vertical direction, one first heat transfer pipe 12 a and one second heat transfer pipe 12 b are arranged alternately. Alternatively, as shown in FIG. 4B, the first heat transfer pipes 12 a and the second heat transfer pipes 12 b may be arranged such that, in the vertical direction, two first heat transfer pipes 12 a and two second heat transfer pipes 12 b are arranged alternately.

Assume a case where the first heat transfer pipes 12 a or the second heat transfer pipes 12 b are unevenly distributed and concentrated in one area along the air inlet face 13. In this case, as described below, when cooling/heating is performed by only one of the heat pumps, the cooling/heating is performed in an uneven manner utilizing only one part of the air-intake-side heat exchanger 3. In this case, air passing through the air-intake-side heat exchanger 3 is partly cooled down or heated up, and thereby unevenness occurs in the heating or cooling of the air. In this respect, the air passing through the air-intake-side heat exchanger 3 can be evenly heated up or cooled down by arranging the first heat transfer pipes 12 a and the second heat transfer pipes 12 b such that, in one direction, one first heat transfer pipe 12 a and one second heat transfer pipe 12 b are arranged alternately, or two first heat transfer pipes 12 a and two second heat transfer pipes 12 b are arranged alternately.

FIGS. 4A and 4B each show the arrangement of the heat transfer pipes 12 a and 12 b, in which vertically adjoining heat transfer pipes 12 a and 12 b are arranged at regular intervals. However, as an alternative, the vertically adjoining heat transfer pipes 12 a and 12 b may be arranged at non-regular intervals. In addition, each of the heat transfer pipes 12 a and 12 b may have a linear shape in the flow direction F of the air-conditioning air.

Operation of Controller Embodiment 1

The controller 8 includes a microprocessor and various sensors, for example. The controller 8 includes a memory as necessary. The controller 8 stores a reference value for an air-conditioning load applied to the heat pump air conditioner 200. The controller 8 compares the air-conditioning load applied to the heat pump air conditioner 200 with the reference value, switches the state of the first compressor 2 a and the second compressor 2 b between an operating state and an operation stopped state, and performs output adjustment. Specifically, if the air-conditioning load applied to the heat pump air conditioner 200 is less than the reference value, the controller 8 stops both the compressors 2 a and 2 b from operating.

If the load applied to the heat pump air conditioner 200 is higher than or equal to the reference value and is great, the controller 8 causes both the compressors 2 a and 2 b to operate, thereby causing the refrigerant to flow into all of the heat transfer pipes 12 a and 12 b. However, if the load applied to the heat pump air conditioner 200 is higher than or equal to the reference value but is small, the controller 8 causes only one of the compressors 2 a and 2 b to operate, thereby causing the refrigerant to flow into either the heat transfer pipes 12 a or the heat transfer pipes 12 b.

Thus, in a case, for example, where the air-conditioning load is higher than or equal to the reference value but is small, the controller 8 may cause only one of the compressors to start operating, thereby performing cooling/heating only by one of the heat pumps. This makes it possible to reduce wasteful energy consumption of the compressors in a case where the air-conditioning load is small, thereby improving the comfortableness and energy efficiency of the cooling/heating.

Embodiment 2

If the load applied to the heat pump air conditioner 200 is higher than or equal to the reference value, the controller 8 may cause the first compressor 2 a and the second compressor 2 b to operate alternately. As a result, the refrigerant flows into the heat transfer pipes 12 a and the heat transfer pipes 12 b alternately. Specifically, while causing the first compressor 2 a to operate, the controller 8 stops the second compressor 2 b, thereby stopping the flow of the refrigerant in the second heat transfer pipes 12 b, and while stopping the first compressor 2 a, the controller 8 causes the second compressor 2 b to operate, thereby causing the refrigerant to flow into the heat transfer pipes 12 b. The order in which the first compressor 2 a and the second compressor 2 b are caused to operate alternately may be inverted during the operation. Further, the controller 8 may adopt an operation pattern in which the heat pumps 5 a and 5 b are sequentially caused, one by one, to start and stop. In this case, from among a plurality of operation patterns in each of which the order of the starting and stopping of the heat pumps 5 a and 5 b is different, the controller 8 may switch from one operation pattern to another when stopping one of the heat pumps.

While the air-intake-side heat exchanger 3 is performing a heating operation, since the compressors 2 a and 2 b are both absorbing heat, the compressors 2 a and 2 b may be frosted if the temperature of external air is low. When the compressors 2 a and 2 b are in the state of being defrosted, the operation performance of the compressors 2 a and 2 b degrades. Therefore, the compressors in the state of being defrosted are caused to temporarily perform a reverse-cycle operation to remove the frost. This operation is hereinafter referred to as a defrosting operation. In a defrosting operation period, the controller 8 refrains from switching the state of the compressors 2 a and 2 b between an operating state and an operation stopped state. The controller 8 switches the state of the compressors 2 a and 2 b between an operating state and an operation stopped state only in a period other than the defrosting operation period. Accordingly, the heating operation of the air-intake-side heat exchanger 3 is not interrupted. Also, it is not necessary to separately install a heater or the like for use in the defrosting operation. It should be noted that an operation performed as the defrosting operation is not limited to the reverse-cycle operation, but may be a different operation. The above-description gives merely one example of the defrosting operation.

Embodiment 3

Alternatively, when causing the first compressor 2 a and the second compressor 2 b to operate alternately, the controller 8 totals either a previous operating time of each of the compressors 2 a and 2 b or the number of previously performed operations of each of the compressors 2 a and 2 b. The controller 8 may preferentially cause one of the compressors 2 a and 2 b with a less previous operating time or a less number of previously performed operations to operate, and may stop the other one of the compressors 2 a and 2 b with a more previous operating time or a more number of previously performed operations. In this manner, the operation frequency or operating time can be made uniform between the compressors 2 a and 2 b. This makes it possible to extend the life of the compressors 2 a and 2 b, and reduce the number of times to repair the compressors 2 a and 2 b due to breakdown.

The controller 8 may switch the state of the compressors 2 a and 2 b between an operating state and an operation stopped state not in the defrosting operation period, but only in a period other than the defrosting operation period.

Embodiment 4

FIG. 5A shows control steps from when the first and second heat pumps 5 a and 5 b are in an operation stopped state to when the outputs of the first and second heat pumps 5 a and 5 b reach their upper limits. The horizontal axis represents time, and the vertical axis represents the output levels of the respective heat pumps 5 a and 5 b. In the example shown in FIG. 5A, first, the second heat pump 5 b is caused to start operating at a time t1, and then the first heat pump 5 a is caused to start operating at a time t2. The output of the second heat pump 5 b increases from the start of the operation in proportion to the elapsed time, and reaches an output S2 immediately before the time t2.

Meanwhile, the output of the first heat pump 5 a at the start of the operation at the time t2 is represented as S1. At the start of the operation of the first heat pump 5 a, i.e., at the time t2, the controller 8 controls the operation of the second heat pump 5 b such that the output of the second heat pump 5 b becomes a value obtained by subtracting S1 from S2. As a result, the sum of the outputs of both the heat pumps 5 a and 5 b at the time t2 becomes S2, which is the same as the output immediately before the time t2. If the output of the second heat pump 5 b at the time t2 remains S2, the sum of the outputs of both the heat pumps 5 a and 5 b is S2+S1, which causes rapid output increase, i.e., overshoot. This causes loss due to uneven cooling/heating or excessive cooling/heating. Therefore, the controller 8 controls the operation of the second heat pump 5 b, such that the output of the second heat pump 5 b at the time t2 becomes a value obtained by subtracting S1 from S2, thereby realizing comfortable air conditioning with no unevenness or loss in cooling/heating.

FIG. 5B shows control steps from when the first and second heat pumps 5 a and 5 b are in an operating state to when the first and second heat pumps 5 a and 5 b become an operation stopped state. In the example shown in FIG. 5B, first, the first heat pump 5 a is caused to operate such that, from a time t3, the output of the first heat pump 5 a decreases from the upper limit output in proportion to the elapsed time. Thereafter, the second heat pump 5 b is caused to operate such that, from a time t4, the output of the second heat pump 5 b decreases from the upper limit output in proportion to the elapsed time. The first heat pump 5 a stops at a time t5, and its output immediately before the stop is S3. That is, at the time t5, the output of the first heat pump 5 a becomes zero from S3. If the output of the second heat pump 5 b keeps decreasing from the time t5, it causes rapid decrease in the sum of the outputs of both the heat pumps 5 a and 5 b, i.e., undershoot. This causes loss due to uneven cooling/heating or excessive cooling/heating.

Therefore, as shown in FIG. 5B, the controller 8 controls the operation of the second heat pump 5 b, such that the output of the second heat pump 5 b at the time t5 becomes a value that has increased by S3. In this manner, when both the heat pumps 5 a and 5 b shift from an operating state to an operation stopped state, comfortable air conditioning with no unevenness or loss in cooling/heating is realized.

As described above, along an air passage, the vaporizing humidifier 6 is disposed downstream of the air-intake-side heat exchanger 3, and the steam humidifier 7 is disposed downstream of the vaporizing humidifier 6. The vaporizing humidifier 6 and the steam humidifier 7 are both connected to the controller 8. The controller 8 is connected also to a humidity sensor (not shown) in the casing 1. The controller 8 stores therein a reference value for humidity.

The controller 8 first causes the vaporizing humidifier 6 to humidify intake air, and then measures the humidity of the intake air by the humidity sensor. The controller 8 compares the measured humidity with the reference value for humidity. If it is determined that the humidifying of the intake air by the vaporizing humidifier 6 is insufficient, the controller 8 may cause the steam humidifier 7 to operate to further humidify the intake air.

Generally speaking, the running cost of a vaporizing humidifier is less than that of a steam humidifier. Therefore, by humidifying the air by the vaporizing humidifier 6 first and then compensating for the shortfall of the humidity by the steam humidifier 7, the cost of humidifying the air can be reduced.

It should be noted that the present invention is not limited to the heat pump air conditioner of the above-described embodiments, and design changes can be made without departing from the spirit of the present invention. For example, in FIG. 1, the air-intake-side heat exchanger 3 is provided inside the casing 1, and both the heat pumps 5 a and 5 b are provided outside the casing 1. However, as an alternative, both the heat pumps 5 a and 5 b may be provided inside the casing 1. Although the heat-source-side heat exchangers 4 a and 4 b are intended for air-source heat pumps, the heat pumps may be water-source heat pumps. Moreover, the number of heat pumps 5 a and 5 b is not limited to two, but may be three or more.

(Other Matters)

The present invention is useful when applied to heat pump air conditioners.

As this invention may be embodied in several forms without departing from the spirit of essential characteristics thereof, the present embodiments are therefore illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   1 casing -   2 a first compressor -   2 b second compressor -   3 air-intake-side heat exchanger -   4 a, 4 b heat-source-side heat exchanger -   5 a first heat pump -   5 b second heat pump -   6 vaporizing humidifier -   7 steam humidifier -   8 controller -   9 a, 9 b decompression mechanism -   10 a, 10 b switching mechanism -   12 a, 12 b heat transfer pipe -   13 air inlet face 200 -   200 heat pump air conditioner 

What is claimed is:
 1. A heat pump air conditioner comprising: an air-intake-side heat exchanger including a plurality of heat transfer pipes through which a refrigerant passes, the heat transfer pipes being arranged in a direction along an air inlet face of the air-intake-side heat exchanger, the air-intake-side heat exchanger being configured to convert intake air into cool air or warm air and supply the cool air or warm air to a space to be air conditioned; a plurality of first and second heat pumps including, at least, a plurality of compressors configured to compress the refrigerant and supply the compressed refrigerant to the heat transfer pipes and a plurality of heat-source-side heat exchangers connected to the respective compressors, the first and second heat pumps sharing the air-intake-side heat exchanger; and a controller configured to switch a state of the compressors between an operating state and an operation stopped state, wherein the controller controls the compressors to switch an operation of each of the compressors between starting and stopping in accordance with a magnitude of an air-conditioning load.
 2. The heat pump air conditioner according to claim 1, wherein among the plurality of heat transfer pipes, a plurality of heat transfer pipes connected to the first heat pump serve as first heat transfer pipes, and a plurality of heat transfer pipes connected to the second heat pump serve as second heat transfer pipes, and the plurality of first heat transfer pipes and the plurality of second heat transfer pipes are arranged such that, in the one direction, one first heat transfer pipe and one second heat transfer pipe are arranged alternately, or two first heat transfer pipes and two second heat transfer pipes are arranged alternately.
 3. The heat pump air conditioner according to claim 1, wherein the controller causes at least a pair of the compressors to operate alternately.
 4. The heat pump air conditioner according to claim 2, wherein the controller causes at least a pair of the compressors to operate alternately.
 5. The heat pump air conditioner according to claim 3, wherein before causing the pair of the compressors to operate alternately, the controller totals either a previous operating time of each of the compressors or the number of previously performed operations of each of the compressors, and the controller preferentially causes one of the compressors with a less previous operating time or a less number of previously performed operations to operate.
 6. The heat pump air conditioner according to claim 4, wherein before causing the pair of the compressors to operate alternately, the controller totals either a previous operating time of each of the compressors or the number of previously performed operations of each of the compressors, and the controller preferentially causes one of the compressors with a less previous operating time or a less number of previously performed operations to operate.
 7. The heat pump air conditioner according to claim 3, wherein the controller switches a state of the pair of the compressors between an operating state and an operation stopped state not in a defrosting operation period, but in a period other than the defrosting operation period.
 8. The heat pump air conditioner according to claim 4, wherein the controller switches a state of the pair of the compressors between an operating state and an operation stopped state not in a defrosting operation period, but in a period other than the defrosting operation period.
 9. The heat pump air conditioner according to claim 1, wherein after causing the second heat pump to start operating, when causing the first heat pump to start operating, the controller controls the operation of the second heat pump to reduce an output of the second heat pump, such that an output of the first heat pump when the first heat pump starts operating is subtracted from the output of the second heat pump, which has already started operating.
 10. The heat pump air conditioner according to claim 2, wherein after causing the second heat pump to start operating, when causing the first heat pump to start operating, the controller controls the operation of the second heat pump to reduce an output of the second heat pump, such that an output of the first heat pump when the first heat pump starts operating is subtracted from the output of the second heat pump, which has already started operating.
 11. The heat pump air conditioner according to claim 1, wherein the controller performs a stop operation of causing the first heat pump to operate such that an output of the first heat pump decreases in accordance with elapse of time, and then causing the second heat pump to operate such that an output of the second heat pump decreases in accordance with elapse of time, and in the stop operation, the controller controls the operation of the second heat pump such that, when the first heat pump stops operating, the output of the second heat pump increases by an amount corresponding to a decrease in the output of the first heat pump, the decrease occurring immediately before the first heat pump stops operating.
 12. The heat pump air conditioner according to claim 2, wherein the controller performs a stop operation of causing the first heat pump to operate such that an output of the first heat pump decreases in accordance with elapse of time, and then causing the second heat pump to operate such that an output of the second heat pump decreases in accordance with elapse of time, and in the stop operation, the controller controls the operation of the second heat pump such that, when the first heat pump stops operating, the output of the second heat pump increases by an amount corresponding to a decrease in the output of the first heat pump, the decrease occurring immediately before the first heat pump stops operating.
 13. The heat pump air conditioner according to claim 1, wherein the plurality of first and second heat pumps have different minimum critical powers from each other.
 14. The heat pump air conditioner according to claim 2, wherein the plurality of first and second heat pumps have different minimum critical powers from each other.
 15. The heat pump air conditioner according to claim 1, further comprising a vaporizing humidifier and a steam humidifier, wherein along an air passage, the vaporizing humidifier is disposed downstream of the air-intake-side heat exchanger, and the steam humidifier is disposed downstream of the vaporizing humidifier, the vaporizing humidifier and the steam humidifier are connected to the controller, and the controller causes the vaporizing humidifier to humidify intake air, and then if the humidifying of the intake air by the vaporizing humidifier is insufficient, causes the steam humidifier to operate to further humidify the intake air.
 16. The heat pump air conditioner according to claim 2, further comprising a vaporizing humidifier and a steam humidifier, wherein along an air passage, the vaporizing humidifier is disposed downstream of the air-intake-side heat exchanger, and the steam humidifier is disposed downstream of the vaporizing humidifier, the vaporizing humidifier and the steam humidifier are connected to the controller, and the controller causes the vaporizing humidifier to humidify intake air, and then if the humidifying of the intake air by the vaporizing humidifier is insufficient, causes the steam humidifier to operate to further humidify the intake air.
 17. The heat pump air conditioner according to claim 1, wherein a cross section of each heat transfer pipe has an ellipsoidal shape.
 18. The heat pump air conditioner according to claim 2, wherein a cross section of each heat transfer pipe has an ellipsoidal shape. 